Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
Department of Disease Biology, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, 2200 Copenhagen, Denmark.
Mol Cell. 2014 May 8;54(3):335-48. doi: 10.1016/j.molcel.2014.03.018. Epub 2014 Apr 10.
The linear ubiquitin (Ub) chain assembly complex (LUBAC) generates Met1-linked "linear" Ub chains that regulate the activation of the nuclear factor κB (NFκB) transcription factor and other processes. We recently discovered OTULIN as a deubiquitinase that specifically cleaves Met1-linked polyUb. Now, we show that OTULIN binds via a conserved PUB-interacting motif (PIM) to the PUB domain of the LUBAC component HOIP. Crystal structures and nuclear magnetic resonance experiments reveal the molecular basis for the high-affinity interaction and explain why OTULIN binds the HOIP PUB domain specifically. Analysis of LUBAC-induced NFκB signaling suggests that OTULIN needs to be present on LUBAC in order to restrict Met1-polyUb signaling. Moreover, LUBAC-OTULIN complex formation is regulated by OTULIN phosphorylation in the PIM. Phosphorylation of OTULIN prevents HOIP binding, whereas unphosphorylated OTULIN is part of the endogenous LUBAC complex. Our work exemplifies how coordination of ubiquitin assembly and disassembly activities in protein complexes regulates individual Ub linkage types.
线性泛素（Ub）链组装复合物（LUBAC）生成 Met1 连接的“线性”Ub 链，调节核因子κB（NFκB）转录因子和其他过程的激活。我们最近发现 OTULIN 是一种特异性切割 Met1 连接的多 Ub 的去泛素化酶。现在，我们表明 OTULIN 通过保守的 PUB 相互作用基序（PIM）与 LUBAC 组件 HOIP 的 PUB 结构域结合。晶体结构和核磁共振实验揭示了高亲和力相互作用的分子基础，并解释了为什么 OTULIN 特异性结合 HOIP PUB 结构域。对 LUBAC 诱导的 NFκB 信号转导的分析表明，OTULIN 需要存在于 LUBAC 上才能限制 Met1-多 Ub 信号转导。此外，LUBAC-OTULIN 复合物的形成受到 PIM 中 OTULIN 磷酸化的调节。OTULIN 磷酸化可阻止 HOIP 结合，而非磷酸化的 OTULIN 是内源性 LUBAC 复合物的一部分。我们的工作说明了在蛋白质复合物中泛素组装和拆卸活动的协调如何调节单个 Ub 连接类型。
